Hollow mystery for Mars rover New Scientist

The Mars rover Spirit has completed its first full set of scientific measurements with the instruments on its robotic arm, revealing mysterious hollow grains in the soil. The one-metre arm used its microscope to take a close-up image of an undisturbed patch of soil next to the NASA rover. It shows mostly sand-sized particles, but with a large number of apparently hollow spheres or tubes. The image resolution is about 30 microns per pixel – about the width of a human hair.